Method and apparatus for drawing sheet glass



July 28, 1925. 1,547,910

E. T,FERNGREN I METHOD AND APPARATUS FOR DRAWING SHEET GLASS n Filed May 2a, l192.2 2 sheets-sheet 1 supply.

Patented July l28, y1925.

ENOCH T. FERNGREN, OF TOLEDO, OHIO,

PATENT OFFICE.

ASSIGNOR T0 THE LIBBEY-OWENS SHEET GLASS COMPANY, OF TOLEDO, OHIO, A CORPORATION OF OHIO.-

METHOD AND APPARATUS FORDRAWING "SHEET GLASS.

Application, filed May 26,

T 0 all whom t may concern! l Be it known that I, ENocH T. FERNGREN.

a citizen of Sweden, residing at Toledo, in

the county of Lucas and State of Ohio, have invented new and useful Improvements in Methods and Apparatus for Drawing Sheet Glass, of which the following is a specification.

This invention .relates to a new and improved method and apparatus for drawing sheet glass. l

In general, the invention involves propressively congealing a surface layer of semi-plastic glass on the upper surface of a body of hot mlten glass, and then floating or sliding off this surface layer in a substantially horizontal direction and drawing;r or stretching it into sheet form before if becomes'entirely. cold and set.

Incidental to the above main obiectg the invention employs certain new forms of cooling devices, and a new system of maintaining a circulation in the reservoir of molten glass, to prevent stagnation and devitrlication at the end remote from the source of Other objects of the invent-ion will vbecome apparent from the detailed description of two types vof :apparatus adapted to carry out the principles of this invention.

In the accompanying drawings:

Fig. l is a vertical longitudinalcentralsection through the main portions of one form of the sheet drawing apparatus.

Fig. 2'is .a view taken at right angles to Fig. l, the viewbeing partly in vertical section on substantially the line 2 2 of Fig. l. and partly in elevation. many of the parts being broken away to facilitate the disclosure.

Fig. 3 is a longitudinal section on line 3-3 of 4, through a portion of the operating mechanism for the edge cooling.

rollers.

Fig. 4 is a section through these edge cooling rollers -and a portion of the adjacent operating mechanism.

Fig. 5 isla sectional perspective view through a portion of one of the cooling devices.

Fig. 6 is a longitudinal section, similar'I to Fig. l, through a modified form ofthe apparatus. The section is taken 'substantially on the line 6-6 of Fig. 7.l F1gw7 is a transverse vertical section,

" of the tank.

1922. Serial No. 563,754.

taken substantially on the line 7 7 of lof the tank, and a supporting and heating chamber 4 surrounds this closedv end of the tank. Suitably arranged burners within this chamber 4 maintain the gla'ss at the closed end of the tank at the proper temperature. The usual practice in sheet-drawing systems is to lallow the whole mass of molten glass to cool to a rather viscous and semisplastic condition before the sheet is drawn therefrom. In the present system, onl the contrary, the main pool or reservoir of molten glass is maintained in a highly heated fluid condition. and a cooling means is applied locally to a portion of thevsurface'ofthe pool, and the surface layer thus congealed is floated or drawn off from the underlying iiuid glass as hereinafter described.

A refractory dam member 5 is suspended in a partly immersed position within ther molten glass, so that the upperl edge .there of forms an elevated ridge over which? the sheet glass is pulled or fioated when drawn from the molten mass of glass 2. The..

length of this dam is less than the width of thetank or reservoir of molten glass, so that side passagesy or streams of molten glass 6 are left at either end of the dam. The dam is also spaced fromthe end wall 7 of the tank a distance about equal to the width of the passages 6, so as toleave, a

body of molten glass 8 between the frontv face of the dam and the end of the'tank. This body of glass 8 connectswith the side streams of glass 6 at the two endeorners Cover tiles9 'and '10 extend over lthe bodies of glass 6 and 8' to-keep these masses of glass-'at the proper .temf' perature. v The rear face 11 of the dam 5 isprefer ably somewhat convex, and substantially* werticalfand the molten glass is banked up aga-inst this'fae, as at 1.2, when the lsheet-of 'glass 13 isdiawn thereoveras ,will be hereinatter described. The front face 14 of the member 5 is preferably somewhat con cave, and such of the iiuid glass as is drawn over the dam, beneath the sheet 13, iiows down this tace 14 into the pool 8 of molten glass in front of the dam. The dam 5 has uptfurned extensions 15 at its ends, which are hung from supporting rods 16, eXtending out through the top ot the housing 17, and through supporting brackets 18. Springs 19 surround the rods '16 between the supporting brackets 18 and nuts 2O screwed on the ends of the rods. In this manner the dam is yieldably supported or floated in the pool of molten lglass, and may yield somewhat and adjust` itm position under unusual strains when the sheet of glass is drawn therecver.

The housing or roof member 17 extends above the' darnv 5, and the adjacent portions of the tank and drawing mechanism, but the sides of this housing are open to the air as shown at 21.

The main body ot the tank or reservior 1, is arched over as shown at 22, and the front of this portion of the chamber is closed by a vertical cross-slab which bridges the space between the rootl 17 and the arch 22, and extends down to the tops of the side cover-tiles 9.

Adjustably suspended at the sides through the arched roof 22 are a pair of shearcakes or slabs 24, of refractory material, spaced some little distance behind the slab 23; and somewhat further back in the chamber is a central hanging slab 25 of approximately the width of the dam 5, or the sheet of glass drawn th'ere'over. These slabs 24 and 25 are suspended from cables 26 and 27 so that their distance above the pool of molten glass may be regulated as found desirable.

Between the 'slab 23' and the slabs 24 and 25 is defined a somewhat irregular cooling chamber 28, cut oil' in a measure from the' heat ot' the main portion of the furnace by the slabs 24 and 25, and within this chamber 28 are located the cooling devices for congealingv a surface layer of viscous semiplastic glass as at 29 upon the surface of the molten pool 2.

' The ma'or cooling element may tane a variety o forms, but is shown at 30 in ]Fig. 1 as a water-cooler having a rather extensivev horizontal lower surface positioned substantially parallel to,"and adjacent, the upper surface of the pool of glass. The water flows in through one of the supporting .pipes 31, which have extensions 32 within the main bodyot the cooler so that the water will be discharged at points adjacent each end thereof, and the water draws out through the other supporting pipe The supporting pipes 31 and 33 extend out through openings 34 in'the sidewalls 35 ot the arched housing 22, and are supported in vunder unusual stress, and thus allow suitable pedestals 36. A circulation of cold Water is maintained through the cooler, and this water absorbs a considerable amount ot the heat from the upper surface portions of the molten glass that flows or is drawn beneath the cooler.

A second, positive, air-cooler 37 is a1'- ranged just ahead of the cooler 30, and between this cooler 30 and thc dam 5. A

section of this c-oolcr is shown in F ig. 5.

Air under pressure is fed in through one or both ot the supporting pipes 38 and 39, these pipes continuing inside of the housing 40, and having a number o'l spaced outlet holes 41 through 'which the air blows out to the interior of the housing. Housing 4() has a bottom slot 42 through which this cooling air will be directed in an even stream or sheet against the congcaling surl'ace sheet of glass as it is drawn beneath the cooler, in a manner presently to be described.

In addition to the above, edge cooling and tensioning elements are used as shown in Figs. 1 and 2, and in detail in Figs. 3 and 4. Each edge of the sheet 13, after it is pulled over the dam 5, passes between a pair ot internally water-coolcd rollers 43. .These rollers have their faces grooved as shown at 44, and each roller is in the form of the frustum of a cone, the narrower end being at the outer edge of the sheet, as shown in Fig. 4. In this way a more secure grip is obtained on thesheet edge portions. The inner end or each roller 43 has formed thereon a spherical bearing surface 45, which is journaled in a spherical seat or bearing in the supporting casing 4G. A gear 47 is also formed about the outer surface of spherical bearing The two gears 47 mesh with one another, and a driving gear 43 meshes with the upper gear 47, so that the two rollers are driven in unison but in opposite directions. `Each roller 43 is hollow and a pipe 49, open at both ends leads in through the rear end of the roller, as shown Vin Fig. 4, and terminates near the outer end of the roller. On the projecting exposed end of the upper pipe 49 is mounted a bearing b lock l 50 which normally contacts with a partition A51 within the casing 46. On the corresponding end of the lower pipe 49 is mounted a Similar `bearing block 52, which normally bears against an adjusting screw 53, and an expansion spring 54 is seated between the two bearing blocks 50 and 52. With this mounting the two rollers 43 are normally held in spaced relation as shown in Fig..4, but may yield apa-rt, Aagainst the spring 54, harder po tions of the glass, or foreign substances tt pass between them, without injury to the mechanism. A circulation of water is maintained through the rollers, and the operating ,1

and supporting members therefon This the chaniber in Which they 'are located,`and

'also acts as a cooling medium for the edge portions of the sheet.. To provide for this water circulation, the casingv Llois divided interioriy into tivo separatechambers 55 and 56 extending substantially the'lengtli oit' the casing. A t the lower end ot the casing, the blocks 50 and 52, land spring 5t. vlie Within a portion of the outer chamber whereas this gears 4&7 and 48 lie inithe inner chamber 56., Water fiows into chamber through pipe 57 from some outside source of supply. It then flows through pipe 4S) to the hollow interior 58 of` the rollers from which it emerges through passages 59, adjacent the spherical bearing surfaces d5, into the inner 'chamber 56, from which the Water eventually iows out through exit pipe 60. Mounted within the chamber 55, on the other end otA the shaft to' Which-is affixed the gear d8, is a sprocket-Wheel (il, driven by sprocket chain 62. The chain 62 runs up through chamber 55 and is carried and driven atthe upper end by a similar sprocketl (not shown) on the end of a cross-shaft 63, mounted in bearings 64 above the roof 17. Both sets of edge coolers are simultaneouslydriven 'ifrora the same shaft 63, and Ythis shaftfis driven through bevel gearing (ifroin-.driveshaft 66. The speed of drive shaft `66 is y adjiustable -so that 4the speeds of ,the edge rolicrs 43 may be varied as desired. f l

In general, the operation consists 1n con-v gealing or solidifying a surface layer of rather sti'i semi-plastic glasslonthe surface ,Y of themolten pool, as the glass'lows or is :drawn beneath the cooling elements 30 .and

I 37 and then oatimr off orl draWinOr oli this surface layer in a substantially horizontal direc-tion and stretching it into its final sheet vtorni. The sheet of glass is drawn olf over and tenacious, some of it will bei-drawn the upper edge ot the dam or oater 5, and since the molten glass issomewhat sluggish along 'with the more viscous surface portion and will bank up behind the dam as at 1 2.

f fis the sheet is drawn over the dam, some Y of this molten or Huid glass Will be drawn over the upper edge or ridge of the dam and flow down into the front pool 8. This fluid glass will serve as a lubricant upon which ythe sheet is floated over th'e'ridge of the dem. The sheet i3 is then drawn ofi' be tween the edge rollers e3, and (in the form shown in Figs. l to' 5) over acooled supe porting roll 67 and through any appropriate crin oi drawing mechanism 68, which may be oit the forni shown in the Colburn Patent.

No. 1,248,809, granted nec. :4, i917. The

05 ledge portionsfof the ledge roilers a3 are 'preferably driven seine-l wha-t slower than the drawing mechanism positively draw .the act naar the dam,ja.nd

at the saine time cool and hqldback some-y u'hat on the edges of the sheet to maintain the width during the stretching operation that takes place after the stillv plastic sheet is drawn over the dani or lioat 5, and Lct'ore itL becomes set in final sheet forni. .i couler 39, 'preferably of 'the internally water;l cooled type, is positioned below the sheet betore it reaches the 4supportin' g roll '6T and insures the lower surface of the sheet being cooled suliiciently not to stick, to the roller, or be marred thereby.

-its the molten glass 2 is continually beingA` and behind the dam 5 must 'fiow back along the sides of the tank, gradually joining the forward central flow .toward the dam and into the sheet. In this Way a continual slow circulation of the Vmolten glass is pro duced, and stagnation and consequent devitrification of the glass vin the front. porn,

@tions of the tank is avoided. l "ng-w A Vsomewhat modified form of apparatus, embodying much the same principles .o'

operation, is shown in Figs. 6 and 7. In

this modication', the tank portions land 3, and theheating chamber 4 are much the saine as in the form lrst'de'sc'ribed. l In this case the dam or 'float 70 is 'supported from beneath -on a pair of pedesta1s'71 whichl project up' from the bottom of -tank extension 3. Of course the dani might, if desired be hung from above as in Figs.A l and 2.

It will be noted in Fig. 7 that lthe dam is' arched upwardly somewhat at the center. This is to correspond in a measure with the surface of theglass' banked up behind the dam which will tend to flow away toward eitherv side as already described Preferably the darn 5, in the previously described construction will be arched in a similar manner.

The main portion of tlie tank is arched over at 22, as in the construction first deand a pair of side partitions 73 and 74, all hung from above -and reaching nearlyto the surface of the moltenl glass 2, define a cooling cli-amber above the molten glass of approximate f the Width of the sheet 13 'to be `drawn from the tank. The front of 'this chamber is adjustably closed by the hangin gate 75. The extreme forward |end of tha tank isarched over at v76 and closed in frdbt by a vsecond adjustable hanging gate llThe temperature of. the

.75:and 7 7 :nay as desired,

scribed. However, a rear partition Wall 7 2,

77. partially.. cloed chamber `78, forniedbetween the gates iso ' or other fluid is fed `is congealed upon means of suitable burners within thechanr bei'. or by adjusting the cooler 79 in or out. The edge cooling rollers -173 may he of the sain-e form shown in Figs. l to Ll, although their operating and supporting structure has been omitted in Figs. (3 and 7.

The major cooling appawdtus, for congenling the surface layer on the molten is in this form of the dei/Tide composed of a series or bank of separate cooling units 80. Each cooler S() comprising' a metallic casing suspended from a pipe 8l adjustable` -vertically through a roof plate 82. A por-l tion of thev pipe 8l is threaded as at 83, and the position of the adjusting nut 84 above plate S2 regulates the proximity of vthe lower end of the cooler to the 'surface of the molten glass. tends centrally through pipe 81, and nearly to the bottom of cooler'80. Cooling water in through pipe 85, and passes out from cooler 8O through pipe 8l. As will be evident from the drawings these cooling units 80 are arranged in a. series of transverse rows across the sheet, and as the elevation of any single unit can be individually adjusted, the cooling ctl'ect on the'surface of pool 2 may be regulated as found` desirable in all parts of the cooling chamber. In some installations, experience may prove it to be unnecessary to have such a large range of adjustment, and a single transverse cooler may be substituted for a row of transverse coolers, more probably those rows most remote from the dam They operationof drawing and forming the sheet of glass 13 is much the same as with the apparatus first described. In this case, the sheet is drawn away from dam in a more truly horizontal direction. It passes from edge rollers 43 between the coolers 79` and S6, which quickly set the sheet, and over supporting rollers 87 into 'the drawing mechanism 68, from which it passes to the annealing leer as in similar installations.

Obviously, 8O shown in Figs.

the form of cooling apparatus G and. 7, could be substituted for-the cooling mechanism 30 shown in Figs. 1 to 4, and vice versa. Also the air-cooler 37 may be. used in either or both forms of apparatus, as may be found necessary under varying conditions to securethe proper degree of semisolid plasticity 1n' the surface layer of glass.

In either form of apparatus, a distinct surface layer of semi-solid tenacious glass the surface of a pool of liquid glass, and then this layer is floated or drawn off over a slightly elevated ridge, and' drawn away in sheet form. As the sheet is continually drawn away, the congealed surface layer is continually replaced as more molten glass flows under the cool it smaller pipe S5 exby fluid gass,

if r

ing elements. In this way` the operation 1s continuous. I asulrcady described, incidentally causes a continuous circulation of the liquid glass toward and away from the closed end of the tank, thus' preventing the accumulation of stagnant glass at any point.

Claims:

1 The .process of drawing sheet glassl which consists in creating 'a oating unit of plastic glass on abody of molten glass, and then drawing a sheet of glass from said plastic unit while maintaining the surface portion of thevmolten body which surrounds'the said unitl in ahighly fluent state.`

Q The method of producing sheet glass which consists in congealing a portion `otthe surface layer on a body of fluid glass to aA point of plastic solidity andy impelling the glass sheet .from this surfaceA layer in a manner to supply one side of the sheet with a coating of the fluid glass.

3. The method of producing sheet glass which consists in congealing a portion of the surface layer on a body of fiuid glass in a tank, and floating this surface layer from the liquid glass without contacting the walls of the tank, while maintaining a circulation of thetluid glass within the tank, first forwardly under and with the sheet, and then back between the sidesof the tank andthe outer edges of the congealed surface layer..

et. The process of drawing a continuous sheet of Glass which consists in locally changing t e iuidit;l in the surface stratum of a body of molten glass to a state of plasticity along a predetermined area central of the molten body, to the plastic stratum to move it and adjacent substratums lengthwise Aof the body while creating a zone of resistance to'said movement transverse of its patlnand causing the formation of a slanting elevation to raise the surface stratum above the normal level of its surrounding body while.

progressively drawing the sheet of glass therefrom.

5. The method of producing sheet glass consisting in congealing a layer or sheet of semi-solid glass on the surface of a pool of molten lass, the sheet being surrounded and floating this sheet of glass o om the pool horizontally.

6. The method of producing sheet glass consisting in congealing a of semi-solid glass'on the surface of a pool of molten glass, floating this sheetof glass horizontally on the fluid glass therebeneath, drawing the sheet'away from the pool, and cooling the surfaces of the sheet as they leave the pool. 7 The methodv of producing sheet vglass consisting in con'jgealing a layer or sheet of semi-solid glass on the surface of a' pool Also this drawing operation;

applying drawing stress layer or sheetY of molten glass, oatin ,this sheet of glassl combination of means for causin the' pro-1 gressive formation of a sheet of p asticnglassv upon a body of fluid glass, means forpro' gressively drawing the Said sheet away from the body, and meansI for causing the building.

up of a supporting'elevationl of fluid glass beneath the plastic sheet where it is drawn from the said body. 'I

9.In a sheet glass drawing device, the

combination ot'I cooling means for progressively congealing a localized-.portion'of the surface layer of a body of molten glass, and means for drawing away laterally this con-l gealed portion in sheet formt 10. 'Iny an apparatus for drawing sheet glass., the combination of means for pro-A gressively causing the formationof a sheet of plastic glass upon the surface of a body of molten glass, means for maintaining an elevated ridge of molten glass within the main the sheet of glass, a receptacle containing la' pool of. -molten glass, and a dam or loater partly body ofglass, and means for drawing off the sheetof plastic glass over the ridge. 11. In an apparatus for drawing sheet glass, the combination with a tank containmg a body of molten glass, of meansy for progressively causing the formation of a sheet of "semi-solid, plastic glass upon the surface of the molten glass, a. dam or float partially submerged in the molten glass in spaced relation to one end 'of the tank, and means for causing a stream of molten glass to flow over the dam and simultaneously floating the sheet of plastic;

glass from the tank on this stream.

12. In an apparatus for drawing sheet glass,` a receptacle containing `a pool of molten glass, and a dam or`oater partly submerged in the molten glass, over which glass is drawn laterally from the ool. p 13. In an apparatus for drawing sheet submerged in the molten glass, in spaced relation to the walls of the 'rece tacle, over which the sheet is drawn. lateral y from the pool.

14. In, an apparatus to; drawing sheet glass, av receptacle containing a pool of suspendedl in a partly submerge glass is drawn aterally 'from the pool.

vcasing'and ro ers. molten glass, and adam or oater'ieldingly i position in the molten Glass, over which the sheet of 15.v An apparatus drawing sheet glass,

'comprising a receptacle for a pool of molten .glassfa dam or float positioned Within the pool of glass, means for congealing a sheetof-glassonwthesurface of the liquid pool,

and means '"forfdrawing the sheet 0E hori- 4 zontally 'over the dani.

16. An apparatus for drawing sheet glass,

comprising a receptacle for molten glass having oneend closed and the otherend'in open communication with a supply of molten glass, a dam `or float positioned within `the pool of glass in spaced relation to the closed end'of the receptacle and projecting somewhat above the normal level of the glass in the receptacle, means for congealing a layer.

or sheet of semi-solid glass on the surface of the pool,l and means for drawing off this sheet horizontally over the dam.

17."v In an apparatus for drawing sheet' lass a.l rece taele containin a mass oi molten glass, and a cooler :tor the surface r glass comprising ayclosely assembled group .of separate units each independently adjust able toward and away from the glass sur-l face. I

18,-In an apparatus for drawing sheet glass, a receptacle containing-a mass of Imolten glass, andfa cooler for the surfacev -glass comprising an assembly Aof separate units independently adjustable toward and away from the glass surface.

'19. In an apparatus for drawingfshe'et glass, .areceptacle containing a mass "of molten glass, and a cooler for the surface" glass comprising a closely assembled group of separate units each independently adjustfj;

able towardand away from the glass sury face, each unit including means' for main-` taining a flow ofcooling fluid therethrough.

20. In an apparatus for drawing sheet glass, a positive coolerwfor the sheet, comprising a casing havinga slot through whichl ratus, a sheet edge cooling mechanism, comprising a suspended casing, a pair of sheet edge gripping rollers horizontally pivoted for rocking adjustment at the lower end of the casing, means `within the casing'forf positively rotating`the rollers, and means for circulatin a cooling uid through the Signed at Toledo, in the county 'of'Lucas -air or similar fluid is directed against the and State 'of Ohio, this 24th day of May, v

192e.t i

ENooH T, FERNGREN. 

